The invention relates to a seat back of a vehicle seat with a seat back frame that has been formed out of a sheet iron blank into a pressed piece of sheet iron and that is provided with a main region as well as with a border oriented transversely to said main region, said border being composed of merging portions, viz., of a top border, a left and a right bent corner border and a left and a right lateral border.
Vehicle seats with seat backs provided with a seat back frame designed as a pressed piece of sheet iron are well known in the art. A pressed piece of sheet iron may be readily realized with great accuracy in industrial scale manufacture, manufacturing may be automatized to a large extent.
The seat back frame gives a seat back mechanical stability. The seat back frame specifically supports the padding pieces of the seat back and generally a headrest as well. It is usually hinged to an underframe of the vehicle seat so as to be pivotally adjustable. In case of a load occasioned by an accident, more specifically in case of a rear impact, it must be capable of absorbing the high acceleration forces that are exerted by a passenger occupying the vehicle seat. A seat back of a seat with integrated seat belt is to be able to absorb high forces due to an accident in case of front impacts as well.
This is where the invention is setting in. It is its object to develop the seat back frame of a seat back in such a manner that it is particularly suited to absorb high acceleration forces occasioned by an accident such as they are particularly generated in the event of accidents involving rear impacts.
In view of the seat back of the type mentioned herein above, this object is solved in that there is provided a left and a right stiffening bead, each of which being located in an upper end region of the lateral border and in the main region a) in the portion of the main region that is directly adjacent said upper end region and b) in the neighborhood of the corresponding corner border.
This bead advantageously allows to reinforce the seat back frame in such a manner that it is capable of absorbing even high forces. The bead is easy to manufacture, it does not require additional piece parts, but only specific arrangements to be made in the press mould. The bead permits to utilize the material of the seat back frame in an intelligent manner. A considerably increased stability is being achieved.
In a preferred embodiment, the bead forms a bead edge between the upper end region of each corresponding lateral border and the directly adjacent portion of the main region, said bead edge being oriented offset with respect to an edge between the corner border and the main region and an edge between the main region and the lateral border underneath the upper end region of the lateral border. Accordingly, this bead edge is offset relative to the normal edge at the junction between the main region and the lateral border. This gives the seat back frame greater stability.
In another preferred embodiment, the pressed piece in the bead is deformed in such a manner that it is offset in the main region in the same direction in which the border protrudes and that it is inwardly offset in the region of the border. As a result thereof, the outer contours of the seat back frame are not affected by the bead. The bead is rather situated within the volume defined by the contours of the unbeaded seat back frame.
In a preferred embodiment, an undisturbed, arch-shaped strip of the main region is provided for between the corner border and the bead. In this embodiment, the bead proved particularly efficient. It stiffens the main region in proximity to the corner border without however actually extending up to the edge where the corner border begins. On the contrary, here, the arch-shaped strip, which can be quite narrow and whose width may merely amount to a few millimeters up to a maximum of 30 mm for example, remains free. It is thereby advantageous to allow said undisturbed, arch-shaped strip to widen toward the upper, free end of the bead. This is particularly true at the top border.
In a preferred embodiment, the sheet iron blank in the bead is offset by approximately 3 to 30 mm, preferably by about 12-18 mm, relative to the undisturbed sheet iron blank and the undisturbed border. Such a contoured section permits to attain the desired increase in stability without the need for great deformations.
In a preferred embodiment, the bead has, in a direction transversal to the top border, that is from the top downward, an extension in length which is about double the length of the upper end region of the lateral border. Accordingly, the bead extends nearly to the top border, but without contacting said top border.
In a preferred embodiment, a lateral bead is additionally provided underneath the bead that has just been discussed, said lateral bead being positioned in spaced relationship from the bead that has just been discussed and being realized in the lateral border and in an adjacent portion of the main region. This lateral bead effects additional stiffening. It preferably extends in a direction transversal to the top border over a distance that approximately equals the corresponding dimension of the bead that has been discussed.